The real magic/genius are trailer brakes, they are electric right, however if they worked the way you would naively assume an electric brake would work, directl

The real magic/genius are trailer brakes, they are electric right, however if they worked the way you would naively assume an electric brake would work, directly operating on the friction surface with an electric solenoid, It would take a huge solenoid and the amperage requirements would quickly exceed what the trailer wiring can provide. so what they do is apply an electromagnet which starts to drag on the side of rotating wheel assembly it uses this drag to push the friction surfaces together, so it takes a surprisingly small magnet to run. most of the force comes from the rotating wheel.